Investigations are continuing in three main areas: definition of human tumor antigens; monitoring immune status in cancer patients; and development and testing of immunotherapeutic techniques in patients with cancer. Serologic means are being used to define human tumor antigens. The tumors being studied are melanomas, sarcomas, and breast carcinomas. Using immune adherence, immunofluorescence, and complement fixation we have been able to define an oncofetal antigen common to many tumors and to fetal tissue and additionally have found sarcoma associated and melanoma associated antigens. Currently, we are investigating the distribution of these antigens, the incidence of antibodies in patients and controls to such antigens, and the biochemical nature of the antigens. Immune responses to these antigens are being monitored during the course of disease to determine if responses to tumor antigens can be indicators of clinical prognosis. Assays for circulating or excreted tumor antigens are being established. Clinical protocols for the use of BCG immunotherapy in melanoma, sarcoma, and lung cancer are being tested. BCG is being used for intralesional injection in patients with melanoma and lung cancer, and as an adjuvant to surgery, chemotherapy, or radiotherapy in patients with melanoma or sarcoma. Clinical results of these trials are being accumulated and correlated to pathological findings and immunological assay results.